Experimental study on black soldier fly (Hermetia illucens L.) larvae hydrothermal liquefaction in methanol-water Co-solvent: Bio-oil yields and properties

In this study, methanol-water co-solvent were utilized as solvents for hydrothermal liquefaction (HTL) of black soldier fly larvae (BSFL) for the preparation of bio-oil to achieve a higher value application of BSFL. The effects of process parameters such as reaction temperature (200–290 °C), methanol-water ratio (0:1–1:0), and methanol participation in the liquefaction reaction (3.50–9.28 wt%) on the yield and properties of bio-oils were examined. The bio-oil produced at 260 °C and a methanol-water ratio of 4:1 had a yield of 68.23%, an HHV of 34.2 MJ kg−1, an O/C ratio of 0.13, and a H/C ratio of 2.39, suggesting their potential for use as renewable energy to replace the fossil energy. When taking into account the consumption of methanol at 260 °C, the bio-oil yield was 48.69%, energy recovery was 65.35%, and energy efficiency was 56.36%. GCMS analyses demonstrated that the main components of the methanol-water ratio of 4:1 bio-oil were esters and hydrocarbons, with fewer amides (1.92%), and its composition was similar to that of biodiesel. Methanol played an important role as a solvent in improving the esterification of the acid with methanol and advancing the alcoholysis of the amide.